Average annual salaries for Silicon Valley technology workers surpassed the $100,000 mark last year, according to a new survey, pushed higher by the strength of the region’s latest boom.

Tech-jobs website operator Dice Holdings Inc. said salaries for software and other engineering professionals in California’s Silicon Valley rose 5.2% to an average $104,195 last year, outstripping the average 2% increase, to $81,327, in tech-workers’ salaries nationwide. It was the first time since Dice began the salary survey in 2001 that the wage barometer broke the $100,000 barrier, said Tom Silver, a Dice senior vice president.

The findings come amid a Web boom that has fueled companies such as Facebook Inc., Zynga Inc. and Twitter Inc. Last year, several of the companies—including LinkedIn Corp. and Zynga—went public, with Facebook poised for an initial public offering this year. Their success has sparked the creation of numerous new start-ups, which in turn has spurred a hiring war for software engineers and others.

In contrast, job growth elsewhere in the nation has remained relatively slow. U.S. employers added 200,000 jobs in December, and the unemployment rate ticked down to 8.5%, its lowest level since early 2009. But it is unclear how sustainable such gains may be.

“There’s a tussle for talent growing in Silicon Valley and employers have to pay up,” said Mr. Silver. Overall, tech-job postings in Silicon Valley on Dice rose to 5,026 earlier this month, up 26% from 3,974 a year ago, he said, even as tech-jobs postings nationwide only rose 11% over the same period.

The hiring boom is evident at SmartRecruiters Inc., a San Francisco start-up that offers a free recruiting tool. Itclosed a $5 million venture-capital financing this month and wants to add 40 employees by this summer, said Chief Executive Jerome Ternynck.

But with many job candidates receiving multiple offers, “the limiting factor is the ability to find the right people,” said Mr. Ternynck. “We’d hire them all tomorrow if we could.”

Silicon Valley’s job-market strength has also had a halo effect on bonuses. Silicon Valley tech-worker bonuses jumped 13% last year to an average $12,450, versus an 8% increase to $8,769 nationwide, according to Dice. Meanwhile, hourly contractor rates in Silicon Valley rose 11% last year to an average $74 an hour, compared with $63 an hour nationally, said Dice.